The invention concerns a method for thermally and/or acoustically insulating buildings, in particular building roofs and outer walls, by inserting webs, i.e., strips, or sheets, i.e. panels of mineral wool, in particular rockwool, between such abutments, beams, studs or rafters, and a foil acting as a vapor guard or barrier being bonded or laminated to one side of the strips or panels, the free longitudinal edge bands of said foil being folded once or more often inward so that at least one longitudinal edge of the strips or panels projects outward beyond the particular folded edge band of the vapor barrier. The strips are wound into a roll or the panels are stacked on each other into packaged units.